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1 1. Department of Integrative Medical Biology, section of Physiology, Umea University, Umea, S-901 87 Umea, Sweden
2 2. Department of Orthopaedic Surgery, Kyorin University School of Medicine, Tokyo, 6-20-2 Shinkawa, Mitaka-shi, 181-8611, Tokyo, Japan
3 3. Department of Integrative Physiology, National Institute for Physiological Sciences, Okazaki, Myodaiji, 444-8585 Okazaki, Japan
* To whom correspondence should be addressed. E-mail: Bror.Alstermark{at}physiol.umu.se.
In the rat, some findings have been taken to suggest the existence of monosynaptic cortico-motoneuronal (CM) connections. Since this connection is believed to be largely responsible for the ability to make independent digit movements in primates and man, it has been inferred that the monosynaptic CM connection in the rat is likewise important for skilled prehension. Comparison of intra- and extracellular recordings from forelimb motoneurones in anaesthetized rats, revealed no monosynaptic CM EPSPs. The fastest descending excitation in forelimb motoneurones was disynaptically mediated via a cortico-reticulospinal pathway and slowly conducted excitation via corticospinal fibres and segmental interneurones. The findings stress the importance of di- and trisynaptic excitatory corticofugal pathways to forelimb motoneurones in the control of skilful digit movements.
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